I. Field of the Invention
The present invention relates generally to devices for separating the liquid component from suspensions such as, for example, slurries or sludge, and more particularly to a belt support grid system for use in sludge filtering devices in which the sludge is carried by a moving perforate conveyor belt whereby the liquid is caused to pass through the conveyor belt and be removed from the slurry.
II. Description of the Prior Art
Continuously operating belt filter presses as such are known in the prior art. Such prior art presses have typically been used for filtering suspensions containing high liquid percentages such as industrial slurries of various types or treated sewage sludge. Such prior art presses typically have an endless filter web or conveyor belt which serves to filter and separate the liquid from the sludge-like material. After the material is initially deposited on a substantially horizontal section of the conveyor belt, a portion of the liquid may be removed by the effects of gravity, with the liquid passing through the perforate conveyor belt as the material is carried by the machine. Some prior art presses include a second conveyor belt which cooperates with the first belt by approaching the first belt at an acute angle so as to define between the two belts a converging area where the sludge material carried by the first belt is retained between the belts and compressed as the two belts are brought together as they move in the same direction.
One such prior art device is disclosed in U.S. Pat. No. 3,951,809 to Kolimar, the device including a pair of endless filter belts which carries the sludge between the belts and through a series of rollers where the liquid is extracted.
Another prior art device is disclosed in U.S. Pat. No. 3,984,329 to Wanzel, where a portion of a sludge filtering device is shown. This device includes a conveyor belt having an initial horizontal portion which carries the sludge away from an entrance point. This portion of the belt is supported by a guide table which is pervious to liquid and permits liquid to pass downwardly through the belt and be discharged below. In this device the guide table includes a series of longitudinal grooves and rows of vertical passages which allows the liquid to flow from the guide table. However, during operation, the liquid often adheres to the underneath side of the conveyor belt, especially where a portion of the belt is substantially horizontal. If this adhering liquid is not removed, it tends to decrease the flow rate of the liquid through the belt. Accordingly, it has been found that efficiency of such liquid extracting devices can be increased if the liquid adhering to the underneath side of the conveyor belt is removed by transverse wear strips or bars. Such wear strips also may serve to support the belt carrying the sludge while allowing the liquid to drain through the belt.
An example of such strips can be seen in U.S. Pat. No. 4,404,099 to Austin. This device discloses an endless band of mesh material extending horizontally between a pair of rollers. This horizontal run portion is supported by a plurality of transversely extending spaced parallel bars which would appear to provide some support as well as guiding the conveyor belt.
Other prior art devices have included individual wear strips or bars to support the underneath side of the conveyor belt. However, such bars have typically been of unitary construction and attached to the device by tightly fitting these bars into slots or other channels formed in the device and held securely in place. After a period of operation, such wear strips or bars become worn due to the conveyor belt constantly riding on the upper surface of each bar. As a result of such severe wear, it is necessary that such bars be frequently replaced. Such replacement has heretofore been quite labor intensive and time consuming. To replace such prior art bars, it was necessary to stop operation of the press for a substantial period of time, remove a major portion of the device in order to gain access to the bars then and remove each entire bar individually. Such removal and replacement required a substantial amount of time and labor in an environment which typically made such work quite unpleasant.
As a result of the shortcomings of the prior art, typified by the above, there has developed and continues to exist a substantial need for a filtering device which includes a support system for the conveyor belt which can be quickly and easily replaced or repaired without substantial labor and expense or without the need for the device to be shut down for long periods of time to replace the support system. Despite this need, and the efforts of others, a filtering device having such a support system has heretofore been unavailable.